Arsenal have identified the Olympiakos defender Kostas Manolas as their leading and most realistic transfer target at centre-back.

Arsène Wenger’s need to add defensive cover intensified on Monday when it emerged that Kieran Gibbs would be out for four weeks with the hamstring injury the left-back sustained in the 2-1 win against Crystal Palace on Saturday.

The knock-on is that Nacho Monreal,regarded by Wenger as potential cover at centre-back, is now needed to start at left-back. It leaves Laurent Koscielny and Per Mertesacker as the only senior and specialist centre-backs in the squad.

The situation is further complicated by the fact that Mertesacker is still not fully match fit following his involvement in Germany’s World Cup win – he did not travel to Turkey on Monday for Tuesday's Champions League match – and Koscielny has been managing a foot injury.

Calum Chambers, the 19-year-old signing from Southampton, has so far provided exemplary cover in the position while Ignasi Miquel and Hector Bellerin also made the journey to Istanbul for the first-leg play-off against Besiktas.

With a trip to Everton on Saturday and the return leg against Besiktas next Wednesday, Wenger’s need has become acute but Manolas, 23, is also regarded as a good long-term option. He would cost around £6million and excelled for Greece at the World Cup, where he was named as one of the best 50 players of the finals.

Although Arsenal would be able to offer a significant pay rise, the key decision for Manolas is whether he wants to leave Olympiakos and risk being only third- or fourth-choice centre-back at Arsenal. Wenger had also looked at more expensive options who could also provide cover to Mikel Arteta and Mathieu Flamini in holding midfield, with Luiz Gustavo and William Carvalho both potentially fitting that profile.

There is also considerable competition for any available centre-back from Manchester United, who refused Arsenal’s proposal of including Phil Jones or Chris Smalling as part of a possible deal for Thomas Vermaelen. Arsenal then agreed to sell Vermaelen to Barcelona but, with Bacary Sagna already departed, they now need senior support at centre-back.